Transformer for electric metal-working apparatus.



No. 783,651. PATENTED FEB. 28, 1905. E. THOMSON.

TRANSFORMER FOR ELECTRIC METAL WORKING APPARATUS. urmunmx nun 1350.4.1003.

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PATENT OFFICE.

ELIHU THOMSON, OF SW AMPSCOTT, MASSACHUSETTS, ASSIGNOR TO THOMSON ELECTRIC WELDING COMPANY, OF LYNN, MASSACHU- SETTS, A CORPORATION OF MAINE.

TRANSFORMER FOR ELECTRIC METAL-WORKING APPARATUS.

SPECIFICATION forming part of Letters Patent No. 783,651, dated February 28, 1905.

Application filed December 4, 1903. Serial No. 183,776- i To all whom, it may concern:

Be it known that I, ELIHU THOMSON, acitizen of the United States, and a resident of Swampscott, in the county of Essex and State of Massachusetts, have invented certain new and useful Improvements in 'lransformers for Electric Metal-\Vorking Apparatus, of which the following is a specification.

My invention relates to that class of electric metal-working apparatus wherein the work is heated by currents of large volume. and low electromotive force obtained from the secondary of a transformer. As heretofore 0perated, this class of apparatus has been supplied with alternating currents for its primary by means of a suitable single-phase generator or supply-circuit, by means of which singlephase alternating currents are caused to pass through the primary and generate the heating-currents for the secondary.

The special object of my invention is to permit the single-phase alternating currents of large volume and low clectromotive force supplied to the work to be generated from the primary action of polyphase currents in such manner that the energy shall be drawn equally from the various phases of the polyphase system, so as not to unbalance said system or cause unequal loading of the same.

To this end my invention consists, essentially, in the combination with a welding or metal-working transformer of a primary coil therefor having its terminals connected, respectively, to two wires of a polyphase system and a connection or connections from intermediate portions of said primary to the remaining wires constituting the transmissioncircuits of said polyphase system.

My invention consists, further, in the com bination with the transformer of an electric metal-working apparatus of an auto-transformer connected to the wires of the transmission-circuits for the polyphase system and having a section connected to the primary of the metal-working transformer.

My invention consists also in other combinations of apparatus and circuits, as hereinafter described.

In the accompanying drawings, Figures 1, 2, and 3 represent my invention diagrammatically.

Referring to Fig. l, S indicates the usual heavy secondary for a metal-working transformcr such, for instance, as a weldersaid secondary being preferably of the usual type, comprising a heavy bar or casting of copper, which in its side receives a suitable primary winding, while its terminals are provided with suitable clamping devices B for holding the work W. P indicates the primary for said transformer. It will be understood that the primary and secondary are carried in the usual way on asuitable iron core-,as well understood in the art. a- 5 (1 indicate the mains or transmission-circuits of a polyphase system of two or three phases. To two of the wires of said system, a c, the terminals of the transformer are connected, while the intermediate wire or circuit of the system is connected to an intermediate portion of the primary winding P. it will be understood that the primary is wound for such voltage as to suit the voltage of the polyphase system. By this arrangement of devices the primary P will take energy without unbalancing or loading the systern from all wires thereof; but the secondary S will carry the usual single-phase alternating current for heating the work.

In the modification of my invention shown in Fig. 2 the winding P of the metal-working transformer is connected to a section of the winding on an auto-transformer or compensator P whose terminals and an intermediate portion are connected to the Wires of the polypbase system, as shown. The section of said auto-transformer which supplies the currents to the primary P of the metalworking transformer preferably consists of a number of heavier turns in the circuit of the remaining portions of the winding P". As will he understood, the windings P are on a closed iron circuit or core, as usual in the art.

In Fig. 3 the coils P are the primary of a transformer and are connected to the wires or circuits of the polyphase system, as already described, and are adapted to the voltage of the system, while the secondary S thereof is proper for the winding of the primary P of the welding-transformer. The dotted line L indicates that a middle connection may be made, if desired, between the coils of Pand S W'hat I claim as my invention is 1. The combination with a weldingor metalworking transformer, of a primary coil therefor havingits terminals connected respectively to two wires of a polyphase system and a con nection or connections from intermediate portions of said primary to the remaining wires constituting the transmission-circuits of said polyphase system, and a secondarysubject to the conjoint action of the sections of primary coil carrying out-of-phase currents so as to be the seat of single-phase currents.

2. The combination with the transformer for an electric metal-working apparatus, of an auto-transformer connected to the wires of the transmission-circuits for the polyphase system and having a section connected to the primary of the metal-working transformer.

3. In an electric metal-Working apparatus,

the combination with a metal-working transformer, of a primary coil connected at its terminals to two wires of a polyphase system and having an intermediate connection to a remaining wire of said system, and means for inductively transferring the energy drawn from the whole system to the work as a singlephase alternating current. Signed at Lynn, in the county of Essex and State of Massachusetts, this 9th day of Novem her, A. i). 1903.

ELIHU THOMSON.

Witnesses:

DUGALD MoK. McKInLor, JOHN A. McMANUs. 

